Publication 1763-RM001C-EN-P - October 2009
308 Process Control Instruction
4. Watch the PV. When the PV starts to change, stop your stopwatch.
Record this value. It is the deadtime.
5. Multiply the deadtime by 4. This value approximates the natural
period. For example, if deadtime = 3 seconds,
then 4 x 3 = 12 seconds (≅ natural period)
6. Divide the value obtained in step 5 by 10. Use this value as the loop
updated time. For example, if:
natural period = 12 seconds, then 12/10 = 1.2 seconds.
Therefore, the value 120 would be entered as the loop update time.
(120 x 10 ms = 1.2 seconds)
7. Enter the following values: the initial setpoint SP value, a reset T
i
of
0, a rate T
d
of 0, a gain K
c
of 1, and the loop update time
determined in step 17.
Set the PID mode to STI or Timed, per your ladder diagram. If STI is
selected, ensure that the loop update time equals the STI time
interval.
Enter the optional settings that apply (output limiting, output alarm,
MaxS - MinS scaling, feed forward).
8. Return to page 305 and complete the tuning procedure starting with
step 4.
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
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